The investigators propose to continue work relating to the mechanism action of prolactin on the porcine ovary. As in the past, this work will be divided into two central lines of investigation, the first of which is a study of the ontogeny of prolactin receptor development in porcine granulosa and luteal cells. The investigators have shown that prolactin receptor activity varies greatly during the reproductive cycle of the pig with maximal activity in cells from the corpus luteum and lesser amounts in mature follicles. To understand the physiological changes in prolactin receptor activity, the investigators propose to study porcine granulosa cells exposed to multiple trophic agents in vitro and to assess the effects of these agents on prolactin binding to specific receptors. The second line of investigation proposed in this project involves quantitation of the effects of prolactin on differentiated function of cultured granulosa and luteal cells in vitro. As part of this line of investigation, the investigators are studying multiple indices of differentiated ovarian function (steroidogenesis, cyclic nucleotide generation, prostaglandin synthesis, polyamine metabolism) and how they are influenced by prolactin and other tropic agents in vitro.